Semiconductor devices, such as transistors and photodiodes, based on silicon have been the standard for the past three decades. However, semiconductor devices based on alternative materials are receiving increasing attention for advantages over silicon-based semiconductor devices, such as higher electron mobility. Semiconductor devices based on group III-V semiconductor materials are one example of such semiconductor devices. A group III-V semiconductor material is a compound that includes at least one group III element and at least one group V element. Examples of group III-V semiconductor materials include gallium nitride (GaN), aluminum gallium nitride (AlGaN), gallium arsenide (GaAs), indium aluminum gallium nitride (InAlGaN), indium gallium nitride (InGaN), and the like.